It is standard practice in present day truck/trailer rigs for the trailer to be equipped with pneumatic operated emergency brakes as well as usual service air brakes. Pressurized air is supplied from the truck to the trailer and is introduced to the emergency brake and service brake system of the trailer. The emergency brake is released only so long as constant pressurized air is supplied to the brake. Pressurized air is also supplied to the service air brakes of the trailer upon application of the truck brake pedals by the truck driver.
It is usual in the art to supply the pressurized air for the emergency brakes of the trailer, and pressurized air for the service air brakes, through separate Nylon coiled Tubing which are intercoupled between connectors on the truck and on the trailer.
A major problem with the prior art nylon coiled tubing is caused by the excessive linear length of tubing required (prior to coiling) to accomplish the desired working length of the assembly. This extra linear length increases the distance of which pressured air must travel to activate the service braking systems resulting in a time delay problem commonly known in the industry as "brake lag". Brake lag (slower trailer brake reaction) is one of the factors contributing to the common "jack knife" accident. Excessive length of tubing is required in the prior art product due to the hardness of the nylon material. Another problem of excessive length is excessive sagging which can cause the tubing to catch on other parts of the truck or trailer.
Another major problem encountered with the prior art Nylon coiled Tubing is that of kinking damage. Coiled brake Tubing are handled frequently and the Nylon Tubing can easily be permanently damaged by kinking during handling or by entanglement with vehicle parts. A kink in a Nylon coiled Tubing remains permanent but not conspicuous. This permanent kinking damage is dangerous since it causes constriction of the Tubing and impedes and even cuts off the flow of pressurized air through the Tubing when the coil is extended (as in normal turning operations).
An object of the present invention is to provide a process for making a safer coiled air Tubing for the purposes described above which can help prevent the too common jack knife accident, and which is constructed of a non-kinking material, and which is capable of an extended trouble free life as compared with the prior art Tubing of the same general type.
The improved coiled air Tubing produced by the process of the invention also have an extended temperature range to -70.degree. F. as compared with the prior art tubes, to obviate cracking in freezing temperatures, and to prevent separation from fittings due to cold temperature shrinkage.
In addition the improved coiled air tubes produced by the process of the invention are softer than the prior art tubes and has improved coiled memory characteristics to prevent excessive pull pressure on the connectors, to increase wear life of the Tubing, and also to eliminate sagging of the coiled Tubing so as to preclude any tendency of the Tubing to catch on other parts of the truck or trailer.
The coiled air Tubing produced by the process of the invention may have a greater wall thickness then the prior art Tubing for maximum reliability in all environments, and to permit lesser linear length prior to coiling per assembly for faster brake reaction and less brake lag.